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Geomorphic and sedimentologic data indicate that the climate of today's hyper-arid Atacama Desert (northern Chile) was more humid during the mid-Pliocene to Late Pliocene. The processes, however, leading to increased rainfall in this period are largely unknown. To uncover these processes we use both global and regional kilometre-scale model experiments for the mid-Pliocene (3.2 Ma). We found that the PMIP4–CMIP6 (Paleoclimate Modelling Intercomparison Project–Coupled Model Intercomparison Project) model CESM2 (Community Earth System Model 2) and the regional model WRF (Weather Research and Forecasting) used in our study simulate more rainfall in the Atacama Desert for the mid-Pliocene in accordance with proxy data, mainly due to stronger extreme rainfall events in winter. Case studies reveal that these extreme winter rainfall events during the mid-Pliocene are associated with strong moisture conveyor belts (MCBs) originating in the tropical eastern Pacific. For present-day conditions, in contrast, our simulations suggest that the moisture fluxes rather arise from the subtropical Pacific region and are much weaker. A clustering approach reveals systematic differences between the moisture fluxes in the present-day and mid-Pliocene climates, both in strength and origins. The two mid-Pliocene clusters representing tropical MCBs and occurring less than 1 d annually on average produce more rainfall in the hyper-arid core of the Atacama Desert south of 20∘ S than what is simulated for the entire present-day period. We thus conclude that MCBs are mainly responsible for enhanced rainfall during the mid-Pliocene. There is also a strong sea-surface temperature (SST) increase in the tropical eastern Pacific and along the Atacama coast for the mid-Pliocene. It suggests that a warmer ocean in combination with stronger mid-tropospheric troughs is beneficial for the development of MCBs leading to more extreme rainfall in a +3 ∘C warmer world like in the mid-Pliocene.

The July 2021 flood in central Europe was one of the five costliest disasters in Europe in the last half century, with an estimated total damage of EUR 32 billion. The aim of this study is to analyze and assess the flood within an interdisciplinary approach along its entire process chain: the synoptic setting of the atmospheric pressure fields, the processes causing the high rainfall totals, the extraordinary streamflows and water levels in the affected catchments, the hydro-morphological effects, and the impacts on infrastructure and society. In addition, we address the question of what measures are possible to generate added value to early response management in the immediate aftermath of a disaster. The superposition of several factors resulted in widespread extreme precipitation totals and water levels well beyond a 100-year event: slow propagation of the low pressure system Bernd, convection embedded in a mesoscale precipitation field, unusually moist air masses associated with a significant positive anomaly in sea surface temperature over the Baltic Sea, wet soils, and steep terrain in the affected catchments. Various hydro-morphodynamic processes as well as changes in valley morphology observed during the event exacerbated the impact of the flood. Relevant effects included, among many others, the occurrence of extreme landscape erosion, rapidly evolving erosion and scour processes in the channel network and urban space, recruitment of debris from the natural and urban landscape, and deposition and clogging of bottlenecks in the channel network with eventual collapse. The estimation of inundation areas as well as the derived damage assessments were carried out during or directly after the flood and show the potential of near-real-time forensic disaster analyses for crisis management, emergency personnel on-site, and the provision of relief supplies. This study is part one of a two-paper series. The second part (Ludwig et al., 2022) puts the July 2021 flood into a historical context and into the context of climate change.

The population in the Lake Victoria Basin (LVB) is affected by extreme weather both on land, where flooding regularly occurs and on the lake, where nightly storms often catch fishermen by surprise. The CORDEX Flagship Pilot Study ELVIC investigates how extreme weather events will evolve in this region of the world and to provide improved information for the climate impact community. Here we evaluate the performance of five regional climate models at convection-permitting resolution and present projections for the future using COSMO-CLM in a pseudo global warming approach. Most substantial systematic improvements were found in metrics related to deep convection in convection-permitting models compared to their coarser scale counterparts. For the future, extreme precipitation and wind gusts are expected to increase over the lake due to an thermodynamically induced increase in water vapor whereas the impacts of weaker meso-scale circulation over the lake and stronger thunderstorm dynamics compensate each other. More compound events are expected for the future during which both rainfall and wind gusts are intense. Interestingly, the mean precipitation is strongly affected by uncertainties in large-scale dynamics whereas thermodynamics dominate extreme precipitation. This might imply that uncertainties in future projected extremes are smaller than those in mean precipitation.

Windstorms (major winter storms) are one of the most important natural hazards in Europe. Despite the large observed socioeconomic losses, the impact of windstorms and its decadal variability is not yet fully understood. This study aims to assess the loss potentials associated with European windstorms and the variability in the wind speed climatology across Europe. We use the 12,500-years LAERTES-EU (LArge Ensemble of Regional climaTe modEl Simulations for EUrope) RCM ensemble to study the spatio-temporal distribution and variability of windstorms over Europe. LAERTES-EU is validated against reanalysis data (ERA5) and available ground-based station observations. The associated windstorm losses are estimated by computing statistics of extreme wind speeds and related indices. Different loss indices are validated using historical loss data from the insurance sector. The results reveal that the loss index (LI) is a good proxy for the estimation of potential losses associated with windstorms across Europe in winter. The derived statistics of extreme windstorms such as return periods (RP) show hardly any change in the severity and frequency of windstorms during the covered period 1900-2028, but a strong decadal variability is apparent.

Heavy precipitation over western Germany and neighboring countries in July 2021 led to widespread floods, with the Ahr and Erft river catchments being particularly affected. Following the event characterization and process analysis in Part 1, here we put the 2021 event in the historical context regarding precipitation and discharge records and in terms of the temporal transformation of the valley morphology. Furthermore, we evaluated the role of ongoing and future climate change on the modification of rainfall totals and the associated flood hazard, as well as implications for flood management. The event was among the five heaviest precipitation events of the past 70 years in Germany. However, consideration of the large LAERTES-EU regional climate model (RCM) ensemble revealed a substantial underestimation of both return levels and periods based on extreme value statistics using only observations. An analysis of homogeneous hydrological data of the last 70 years demonstrated that the event discharges exceeded by far the statistical 100-year return levels. Nevertheless, the flood peaks at the Ahr river were comparable to the reconstructed major historical events of 1804 and 1910, which were not included in the flood risk assessment so far. A comparison between the 2021 and past events showed differences in terms of the observed hydro-morphodynamic processes which enhanced the flood risk due to changes in the landscape organization and occupation. The role of climate change and how the 2021 event would unfold under warmer or colder conditions (within a −2 to +3 K range) was considered based on both a pseudo global warming (PGW) model experiments and the analysis of an RCM ensemble. The PGW experiments showed that the spatial mean precipitation scales with the theoretical Clausius–Clapeyron (CC) relation, predicting a 7 % to 9 % increase per degree of warming. Using the PGW rainfall simulations as input to a hydrological model of the Ahr river basin revealed a strong and non-linear effect on flood peaks: for the +2 K scenario, the 18 % increase in areal rainfall led to a 39 % increase of the flood peak at gauge Altenahr. The analysis of the high-resolution convection-permitting KIT-KLIWA RCM ensemble confirmed the CC scaling for moderate spatial mean precipitation but showed a super CC scaling of up to 10 % for higher intensities. Moreover, the spatial extent of such precipitation events is also expected to increase.

Geomorphic and sedimentologic data indicate that the climate of today’s hyper-arid Atacama Desert (Northern Chile) was more humid during the Mid-to Late Pliocene. The processes, however, leading to increased rainfall in this period are largely unknown. To uncover these processes we use both global and regional kilometre-scale model experiments for the mid-Pliocene (3.2 Ma BP). We found that the PMIP4-CMIP6 model (CESM2) and the regional model (WRF) used in our study simulate more rainfall in the Atacama Desert for the mid-Pliocene in accordance to proxy data, mainly due to stronger extreme rainfall events in winter. Case studies reveal that these extreme winter rainfall events during the mid-Pliocene are associated with strong moisture conveyer belts (MCBs) originating in the tropical East Pacific. For present-day conditions, in contrast, our simulations suggest that the moisture fluxes rather arise from the subtropical Pacific region and are much weaker. A clustering approach reveals systematic differences between the moisture fluxes in the present-day and mid-Pliocene climates, both in strength and origins. The two mid-Pliocene clusters representing tropical MCBs and occurring less than one day per year on average produce more rainfall in the hyper-arid core of the Atacama Desert south of 20° S than what is simulated for the entire present-day period. We thus conclude that MCBs are mainly responsible for enhanced rainfall during the mid-Pliocene. There is also a strong SST increase in the tropical East Pacific and along the Atacama coast for the mid-Pliocene. It suggests that a warmer ocean in combination with stronger mid-tropospheric troughs is beneficial for the development of MCBs leading to more extreme rainfall in a +3 K warmer world like in the mid-Pliocene.

While automation helps to increase load-shifting, the combination of automation with time-of-use (TOU) or critical-peak prices (CPP) may lead to rebound peaks at the beginning of low-tariff periods which may exceed the original peak. Using a discrete choice experiment with a representative sample of 696 Swiss consumers, we find that a tariff menu including (i) a flat price with direct load control (DLC) and (ii) a time-of-use tariff without direct load control could avoid this problem. The majority (57%) of mostly younger customers, which could be interested in automation would likely sign up for a DLC with flat prices, while the remaining customers would either chose a TOU tariff with manual load control (28%) or avoid any form of load-shifting incentives (15%).

The CORDEX Flagship Pilot Study ELVIC (climate Extremes in the Lake VICtoria basin) was recently established to investigate how extreme weather events will evolve in this region of the world and to provide improved information for the climate impact community. Here we assess the added value of the convection-permitting scale simulations on the representation of moist convective systems over and around Lake Victoria. With this aim, 10-year present-day model simulations were carried out with five regional climate models at both PARameterized (PAR) scales (12-25km) and Convection-Permitting (CP) scales (2.5-4.5km), with COSMO-CLM, RegCM, AROME, WRF and UKMO. Most substantial systematic improvements were found in metrics related to deep convection. For example, the timing of the daily maximum in precipitation is systematically delayed in CP compared to PAR models, thereby improving the agreement with observations. The large overestimation in the total number of rainy events is alleviated in the CP models. Systematic improvements were found in the diurnal cycle in Top-Of-Atmosphere (TOA) radiation and in some metrics for precipitation intensity. No unanimous improvement nor deterioration was found in the representation of the spatial distribution of total rainfall and the seasonal cycle when going to the CP scale. Furthermore, some substantial biases in TOA upward radiative fluxes remain. Generally our analysis indicates that the representation of the convective systems is strongly improved in CP compared to PAR models, giving confidence that the models are valuable tools for studying how extreme precipitation events may evolve in the future in the Lake Victoria basin and its surroundings.

The Atacama Desert in Northern Chile is considered to be the driest warm desert on Earth. However, its hyper-aridity was punctuated by more humid phases in the past. A prominent paleoclimate period of increased rainfall is the warm Pliocene (ca. 5.3 to 2.6 Ma before present). The processes leading to this rainfall increase are not well understood. While recent studies propose regions Southwest or East of the Atacama Desert as moisture sources for enhanced rainfall, the tropical South-eastern Pacific has so far been overlooked as a potential source. The goal of this study is to identify potential key drivers for the increased rainfall in the Pliocene. With this aim, we have downscaled PMIP4-CMIP6 mid-Pliocene (3.2Ma) and historical (1985-2014) experiments using the regional climate model WRF with a spatial resolution of 10 km. The mid-Pliocene WRF simulation exhibits increased mean annual rainfall in the hyper-arid core of the Atacama Desert when compared with the historical period consistent with paleo-records. This increase can be attributed to frequent intense rainfall events in austral winter during the mid-Pliocene, often associated with strong upper-level moisture conveyer belts (MCBs) originating in the tropical Southeast Pacific in front of mid-tropospheric troughs. In present-day climate, such MCBs are much weaker and mostly originate from the relatively dry subtropics producing less moisture advection. Our clustering of upper-level moisture fluxes uncovers systematic differences between MCBs in the mid-Pliocene and the present-day climate: for the mid-Pliocene we found clusters of strong MCBs from the tropical Pacific, that do not occur under present-day conditions. This is due to stronger troughs off the Atacama Desert paired with warmer sea-surface temperatures in the tropical Eastern Pacific and along the northwest coast of South America during the mid-Pliocene, which are favourable for the development of MCBs. The winter rainfall amount associated with MCBs in the mid-Pliocene far exceeds the present-day total rainfall amount. We therefore conclude that tropical MCBs are a key driver for increased rainfall in the Atacama Desert and should be assessed for future climate. This will require kilometre-scale simulations to resolve the dynamical processes involved.

The structural uncertainty of a climate model is defined as the range of outcomes that can be obtained through different representations of physical processes of the climate system, the selection of different unconstrained parameter values and different choices for the numerical solution of underlying fundamental equations. Exploring the range of these outcomes with the goal of determining a model configuration that produces results in closer agreement with observational data is defined as model calibration or tuning.In this study, the preliminary results of the Coordinated Parameter Testing 2 (COPAT2) initiative of the CLM-Community are presented. In COPAT2, volunteer members of the community join forces together, with the objective of testing and providing recommended configurations for the new and final version of COSMO-CLM (6.0), as well as for the newly released regional climate model ICON-CLM, for climate modeling applications over the European CORDEX domain. A series of sensitivity tests is performed in which various configurations of the models are explored. The aspects that are tested have been carefully selected, based on expert judgment. In the case of COSMO-CLM 6.0, the primary focus is on newly introduced and recently updated parameterizations and physical schemes. For ICON-CLM, these tests are the first ever conducted with the climate version of the model and are based on the operational configuration and on information of experiments performed for the development of the NWP mode of ICON.The simulations are conducted at a horizontal resolution of approximately 12 km over Europe, using ERA5 reanalysis data as boundary conditions. In a first step, a series of relatively short tests is conducted over a 7-year period, from 1979 to 1985. Successively, depending on the sensitivity of the model to the applied changes in its configuration, a sub-set of simulations is extended over a total period of 12 years. The results are systematically analyzed with an evaluation suite that has been further developed and extended for COPAT2. The standardized analysis and condensation of results in very few indices summarizing the models performance allow for an easy and fast comparison of the quality of the different simulations. Beside introducing preliminary results of the conducted sensitivity tests, an overview of the calibration strategy followed in COPAT2 will be presented, including information on the selected metrics, employed observational data sets and further details inherent to the ranking of the different experiments.

The past as an analogue for the future is one of the main motivations to use climate models for paleoclimate applications. Assessing possible model limitations in simulating past climate changes can lead to an improved understanding and representation of the response of the climate system to changes in the forcing, setting the basis for more reliable information for the future. In this study, the regional climate model (RCM) COSMO-CLM is used for the investigation of the mid-Holocene (MH, 6000 years ago) European climate, aiming to contribute to the solution of the long-standing debate on the reconstruction of MH summer temperatures for the region, and gaining more insights into the development of appropriate methods for the production of future climate projections. Two physically perturbed ensembles (PPEs) are first built by perturbing model physics and parameter values, consistently over two periods characterized by different forcing (i.e., the MH and pre-industrial, PI). The goal is to uncover possible processes associated with the considered changes that could deliver a response in MH summer temperatures closer to evidence from continental-scale pollen-based reconstructions. None of the investigated changes in model configuration produces remarkable differences with respect to the mean model behavior. This indicates a limited sensitivity of the model to changes in the climate forcing, in terms of its structural uncertainty. Additional sensitivity tests are further conducted for the MH, by perturbing the model initial soil moisture conditions at the beginning of spring. A strong spatial dependency of summer near-surface temperatures on the soil moisture available in spring is evinced from these experiments, with particularly remarkable differences evident over the Balkans and the areas north of the Black Sea. This emphasizes the role of soil–atmosphere interactions as one of the possible drivers of the differences in proxy-based summer temperatures evident between northern and southern Europe. A well-known deficiency of the considered land scheme of COSMO-CLM in properly retaining spring soil moisture, confirmed by the performed tests, suggests that more attention should be paid to the performance of the soil component of climate models applied to this case study. The consideration of more complex soil schemes may be required to help bridging the gap between models and proxy reconstructions. Finally, the distribution of the PPEs with changes in model configuration is analyzed for different variables. In almost all of the considered cases the results show that what is optimal for one period, in terms of a model configuration, is not the best for another characterized by different radiative forcing. These results raise concerns about the usefulness of automatic and objective calibration methods for RCMs, suggesting that a preferable approach is the production of small PPEs that target a set of model configurations, properly representing climate phenomena characteristic of the target region and that will be likely to contain the best model answer under different forcing., Climate of the Past, 18 (4), ISSN:1814-9324, ISSN:1814-9332

During the Last Glacial Maximum (LGM), a very cold and dry period around 26.5–19 kyr BP, permafrost was widespread across Europe. In this work, we explore the possible benefit of using regional climate model data to improve the permafrost representation in France, decipher how the atmospheric circulation affects the permafrost boundaries in the models, and test the role of ground thermal contraction cracking in wedge development during the LGM. With these aims, criteria for possible thermal contraction cracking of the ground are applied to climate model data for the first time. Our results show that the permafrost extent and ground cracking regions deviate from proxy evidence when the simulated large-scale circulation in both global and regional climate models favours prevailing westerly winds. A colder and, with regard to proxy data, more realistic version of the LGM climate is achieved given more frequent easterly winds conditions. Given the appropriate forcing, an added value of the regional climate model simulation can be achieved in representing permafrost and ground thermal contraction cracking. Furthermore, the model data provide evidence that thermal contraction cracking occurred in Europe during the LGM in a wide latitudinal band south of the probable permafrost border, in agreement with field data analysis. This enables the reconsideration of the role of sand-wedge casts to identify past permafrost regions.

Late Marine Isotope Stage (MIS) 3 and MIS 2 loess–palaeosol sequences in Western Europe comprise alternating loess layer and 3- to 30-cm-thick bleached soil horizons with Fe–Mn oxide precipitations, which are usually interpreted as waterlogged active layers and referred to as ‘tundra gleys’. Active layer thickness data derived from a regional climate model simulation and the fossils (shells, earthworm granules) found in ‘tundra gleys’ argue against such an assumption. Most of these horizons better correspond to Fe-depleted, slightly humic topsoil horizons or subsurface eluvial horizons and should be referred to as (incipient) Ag or Eg horizons. They formed during climate ameliorations associated with vegetation (cryptogams, herbs) development, possibly limited by long-lasting snow cover. Strong mixing usually occurred in these horizons due to the activity of anecic earthworms and frost activity.

Enduring and extensive heavy precipitation associated with widespread river floods are among the main natural hazards affecting Central Europe. Since such events are characterized by long return periods, it is difficult to adequately quantify their frequency and intensity solely based on the available observations of precipitation. Furthermore, long-term observations are rare, not homogeneous in space and time, and thus not suitable to run hydrological models (HMs) with respect to extremes. To overcome this issue, we make use of the recently introduced LAERTES-EU (LArge Ensemble of Regional climaTe modEl Simulations for EUrope) data set, which is an ensemble of regional climate model simulations providing over 12.000 simulated years. LAERTES-EU is adapted for the use in an HM to calculate discharges for large river basins by applying a quantile mapping with a fixed density function to correct the mainly positive bias in model precipitation. The Rhine basin serves as a pilot area for calibration and validation. The results show clear improvements in the representation of both precipitation (e.g., annual cycle and intensity distributions) and simulated discharges by the HM after the bias correction. Furthermore, the large size of LAERTES-EU improves the statistical representativeness also for high return values above 100 years of discharges. We conclude that the bias-corrected LAERTES-EU data set is generally suitable for hydrological applications and posterior risk analyses. The results of this pilot study will soon be applied to several large river basins in Central Europe.

During the Last Glacial Maximum (LGM), a very cold and dry period around 26.5 to 19 thousand years ago, permafrost was widespread across Europe. In this work, we evaluate the potential of regional climate model simulations to reconstruct the permafrost distribution in western Europe during the LGM. With this aim, criteria for possible thermal contraction cracking of the ground are applied to climate model data for the first time. These criteria serve as a precondition for the development of ice and sand wedges, which are a common proxy for past permafrost. Our results show that the permafrost and ground cracking distribution in Europe during the LGM are not consistent with a large-scale circulation with prevailing westerly winds. However, a colder and with regard to proxy data more realistic version of the LGM climate is achieved given more frequent easterly winds conditions. Whereas the permafrost extent and ground cracking regions in the global climate model simulation deviate from proxy evidence, they are in good agreement in the regional counterpart. Given the appropriate forcing, an added value of the regional climate model simulation can thus be achieved. Furthermore, the model data provide evidence that thermal contraction cracking occurred in Europe during the LGM also south of the probable permafrost border. This enables the reconsideration of the significance of ice wedge pseudomorphs and sand wedge casts to understand past climate variations.

Extreme weather events, such as heavy precipitation, hail storms, heat waves, droughts and strong wind gusts have a detrimental impact on East African societies. The Lake Victoria Basin (LVB) is especially vulnerable, due to a large and growing population at risk from flooding. Moreover, nightly storms on the lake often catch fishermen by surprise. As the frequency and intensity of weather and climate extremes in the region is projected to further increase substantially with climate change, so do the risks. This has potentially major consequences for livelihoods and policy. The ultimate aim of the CORDEX Flagship Pilot Study ELVIC (Climate Extremes in the Lake Victoria Basin) is therefore to investigate how extreme weather events will evolve in the future in the LVB and to provide improved information to the impact community. ELVIC brings together different research groups that perform simulations with multiple high-resolution regional climate models operating at the convection-permitting scale (CPS) (https://ees.kuleuven.be/elvic). As a first step towards this overall goal, the added value of the CPS on the representation of deep convective systems in Equatorial Africa is assessed. For this purpose, 10-year present-day model simulations were carried out with five regional climate models at both parameterized and convection-permitting scales, namely COSMO-CLM, RegCM, AROME, WRF and MetUM . Similarly to other regions in the world, there is no unanimous improvement nor deterioration in the representation of the spatial distribution of total rainfall and the seasonal cycle when going to the CPS. Moreover, substantial biases in the multi-annual averages (up to 30 W m-2) and seasonal cycle in Top-Of-Atmosphere (TOA) upward radiative fluxes remain, both in some models with parameterized and with explicitly resolved convection. Most substantial systematic improvements were found in the representation of the diurnal cycle in precipitation, the diurnal cycle in TOA radiation, some metrics for precipitation intensity and number of rain events. More specifically, the timing of the daily maximum in precipitation is systematically delayed when going to the CPS, thereby improving the agreement with observations. In particular, peaktime of precipitation strongly improves over land, especially at the shores of the lake, indicative of a better representation of the impact of the lake-land-mountain circulations on the convection at CPS. The underestimation in the 90th rainfall quantile of three-hourly precipitation in the parameterized models is alleviated. For the 95th and 99th percentile of precipitation no clear improvement nor deterioration is found, which might be related to poor observational constraints on extreme precipitation. The large overestimation in the total number of rainy events is alleviated when going to the CPS. The diurnal range in the radiative fluxes at the TOA strongly improves when going to CPS, especially for the longwave. All this indicates that the representation of the convective systems is strongly improved when going to CPS, giving confidence that the models are a valuable tool for studying how extreme precipitation events evolve in the future in the LVB.

Enduring and extensive heavy precipitation associated with widespread river floods are among the main natural hazards affecting Central Europe. Since such events are characterized by long return periods, it is difficult to adequately quantify their frequency and intensity solely based on the available observations of precipitation. Furthermore, long-term observations are rare, not homogeneous in space and time, and thus not suitable to run hydrological models (HMs). To overcome this issue, we make use of the recently introduced LAERTES-EU (LArge Ensemble of Regional climaTe modEl Simulations for EUrope) data set, which is an ensemble of regional climate model simulations providing 12.000 simulated years. LAERTES-EU is adapted and applied for the use in an HM to calculate discharges for large river catchments in Central Europe, where the Rhine catchment serves as the pilot area for calibration and validation. Quantile mapping with a fixed density function is used to correct the bias in model precipitation. The results show clear improvements in the representation of both precipitation (e.g., annual cycle and intensity distributions) and simulated discharges by the HM after the bias correction. Furthermore, the large size of LAERTES-EU improves the statistical representativeness also for high return values of precipitation and discharges. While for the Rhine catchment a clear added value is identified, the results are more mixed for other catchments (e.g., the Upper Danube).

Extratropical cyclones, a major phenomenon of the mid‐latitude atmospheric dynamics, show strong variability over a range of time scales. Future projections hint at an increase of cyclonic intensity and the associated precipitation, an important fact to be considered when developing future risk assessments. This review presents a first overview of studies which (a) puts the current variability and projected future climate changes of extratropical cyclone characteristics in a long‐term perspective, (b) shows connections to natural external forcings, and (c) deepens our understanding of cyclone intensification processes for past climate periods. We summarize the current state of knowledge for two periods in the past—the last millennium and the Last Glacial Maximum (LGM, 21,000 years ago). For these two periods, the sparse information from paleo proxy archives are compared to climate modeling results on global and regional scales. For example, strong changes of the climate mean state, induced by orbital forcing and associated feedbacks, show strong effects on different cyclone characteristics, for example, a southward shift of the storm tracks over the North Atlantic during the LGM. Other findings indicate that dynamic processes could play at least an equally important role as thermodynamic processes for the variations of cyclone‐induced precipitation. This is in contrast to the projected future changes in cyclone‐related precipitation, which are driven primarily by thermodynamic processes. The review demonstrates how a paleoclimatic view can foster an extended process understanding and be instrumental to better understand future changes in extratropical cyclones and associated characteristics. This article is categorized under: Paleoclimates and Current Trends > Modern Climate Change

s & presentations / EGU General Assembly 2021 EGU General Assembly 2021, vEGU21, online, 19 Apr 2021 - 30 Apr 2021; Göttingen : Copernicus Gesellschaft mbH EGU21-5227, 1 Seite (2021). doi:10.5194/egusphere-egu21-5227, Published by Copernicus Gesellschaft mbH, Göttingen

s & presentations : EGU General Assembly 2021 / European Geosciences Union. General Assembly EGU General Assembly 2021, vEGU21, online, 19 Apr 2021 - 30 Apr 2021; Göttingen : Copernicus Gesellschaft mbH EGU21-4345, 2 Seiten (2021). doi:10.5194/egusphere-egu21-4345, Published by Copernicus Gesellschaft mbH, Göttingen

Earth system models show wide disagreement when simulating the climate of the continents at the Last Glacial Maximum (LGM). This disagreement may be related to a variety of factors, including model resolution and an incomplete representation of Earth system processes. To assess the importance of resolution and land-atmosphere feedbacks on the climate of Europe, we performed an iterative, asynchronously coupled land-atmosphere modelling experiment that combined a global climate model, a regional climate model, and a dynamic vegetation model. The regional climate and land cover models were run at high (18 km) resolution over a domain covering the ice-free regions of Europe. Asynchronous coupling between the regional climate model and the vegetation model showed that the land-atmosphere coupling achieves quasi-equilibrium after four iterations. Modelled climate and land cover agree reasonably well with independent reconstructions based on pollen and other paleoenvironmental proxies. To assess the importance of land cover on the LGM climate of Europe, we performed a sensitivity test where we used LGM climate but present day land cover as boundary conditions. These simulations show that the LGM land-atmosphere feedback leads to colder and drier conditions around the Alps and a warmer and drier climate in southeastern Europe. Even in mid-latitude Europe where the land-atmosphere coupling strength is generally weak, and under glacial conditions with a southward displacement of the storm track and increased importance of the Atlantic, regional climate is significantly influenced by land cover.

The role of environmental change in the evolution of cultural traits is a topic of long-standing scientific debate with strongly contrasting views. Major obstacles for assessing environmental impacts on the evolution of material culture are the fragmentary nature of archaeological and – to a somewhat lesser extent – geoscientific archives and the insufficient chronological resolution of these archives and related proxy data. Together these aspects are causing difficulties in data synchronization. By no means does this paper attempt to solve these issues, but rather aims at shifting the focus from demonstrating strict chains of causes and events to describing roughly contemporaneous developments by compiling and comparing existing evidence from archaeology and geosciences for the period between 40 and 15 ka in Central Europe. Analysis of the archaeological record identifies five instances at around 33, 29, 23.5, 19, and 16 ka, for which evidence suggests an increased speed of cultural evolution. By comparing data from different geoscientific archives, we discuss whether or not these instances have common characteristics. We stress that common characteristics per se are no proof of causality; repeated co-occurrences of certain features over long periods of time, however, suggest that certain explanations may be more plausible than others. While all five cases roughly coincide with pronounced and rapid environmental changes, it is also observed that such conditions do not necessarily trigger major changes in the material culture. Increases and decreases in the diversity of cultural traits seem to be rather correlated with the overall demographic development. In compiling and comparing our data, we also identify periods with high need and potential for future research regarding the relation between environmental change and cultural evolution.

Extratropical cyclones are a dominant feature of the mid-latitudes, as their passage is associated with strong winds, precipitation, and temperature changes. The statistics and characteristics of extratropical cyclones over the North Atlantic region exhibit some fundamental differences between present day (PI) and Last Glacial Maximum (LGM) climate conditions. Here, the statistics are analysed based on results of a tracking algorithm applied to global PI and LGM climate simulations. During the LGM, both the number and the intensity of detected cyclones was higher compared to PI. In particular, increased cyclone track activity is detected close to the Laurentide ice sheet and over central Europe. To determine changes in cyclone characteristics, the top 30 extreme storm events for PI and LGM have been simulated with a regional climate model and high resolution (12.5 km grid spacing) over the eastern North Atlantic and Western Europe. Results show that LGM extreme cyclones were characterised by weaker precipitation, enhanced frontal temperature gradients, and stronger wind speeds than PI analogues. These results are in line with the view of a colder and drier Europe, characterised by little vegetation and affected by frequent dust storms, leading to reallocation and build-up of thick loess deposits in Europe.

In this work, we present different aspects of the mineral dust cycle dynamics and the linkage to loess deposits during the Last Glacial Maximum (LGM) in Europe. To this aim, we simulate the LGM dust cycle at high resolution using a regional climate-dust model. The simulated dust deposition rates are found to be comparable with the mass accumulation rates of the loess deposits determined from Loess sites across Europe. In contrast to the present-day prevailing westerlies, easterly wind directions (36 %) and cyclonic regimes (22 %) were dominant circulation patterns over central Europe during the LGM. This supports the hypothesis that recurring east sector winds, dynamically linked with a high-pressure system over the Eurasian ice sheet (EIS), are an important component for the dust transport from the EIS margins towards the central Europe loess belt. Our simulations reveal the occurrence of highest dust emission rates in Europe during summer and autumn, with the highest emission rates located near the southernmost EIS margins corresponding to the present-day German-Polish border region. Coherent with the persistent easterlies, westwards running dust plumes resulted in high deposition rates in western Poland, northern Czechia, the Netherlands, the southern North Sea region and on the North German Plain including adjacent regions in central Germany. Further, a detailed analysis of the characteristics of LGM cyclones shows that they were associated with higher wind speeds and less precipitation than their present-day counterparts. These findings highlight the importance of rapid and cyclic depositions by cyclones for the LGM dust cycle. The agreement between the simulated deposition rates and the mass accumulation rates of the loess deposits corroborates the proposed LGM dust cycle hypothesis for Europe.

Extreme weather events, like heavy precipitation, heat waves, droughts and wind storms have a detrimental impact on East African societies. The Lake Victoria Basin (LVB) is especially vulnerable, since nightly storms on the lake catch fishermen by surprise. As the frequency and intensity of climate extremes is projected to further increase substantially with climate change, so do the risks, with potentially major consequences for livelihoods and policy in the LVB.The ultimate aim of the ELVIC CORDEX-FPS is to investigate how extreme weather events evolve in the future in the LVB and to provide improved probabilistic information to the impact community. ELVIC (Climate Extremes in the Lake Victoria Basin) brings together different research groups that perform simulations with multiple high-resolution regional climate models operating at the convection-permitting scale (CPS) (https://ees.kuleuven.be/elvic).As a first step towards this overall goal, the added value of the CPS on the representation of deep convective systems in Equatorial Africa was assessed. For this purpose, 10-year present-day model simulations were carried out with five regional climate models both at the CPS and at the scale where convection was parameterized, namely COSMO-CLM, RegCM, HCLIM-AROME, WRF and the Met Office Unified Model. From a comparison of model output with different observational products, no robust improvement was found for seasonal average meteorological variables. Moreover, the change in the seasonal precipitation when going to CPS differs between the models. A robust improved performance was found for deep convection, reflected in an improved representation of the daily precipitation cycle. Preliminary results also point towards an improvement in the representation of extreme precipitation. This suggests that regional climate model simulations at the convection-permitting scale are indeed relevant to assess the climate sensitivity of extreme precipitation in the Lake Victoria Basin.

Extratropical cyclones are a dominant feature of the mid-latitudes, as their passage is associated with strong winds, precipitation, and temperature changes. The statistics and characteristics of extratropical cyclones over the North Atlantic region exhibit some fundamental differences between Pre-Industrial (PI) and Last Glacial Maximum (LGM) climate conditions. Here, the statistics are analysed based on results of a tracking algorithm applied to global PI and LGM climate simulations. During the LGM, both the number and the intensity of detected cyclones was higher compared to PI. In particular, increased cyclone track activity is detected close to the Laurentide ice sheet and over central Europe. To determine changes in cyclone characteristics, the top 30 extreme storm events for PI and LGM have been simulated with a regional climate model and high resolution (12.5 km grid spacing) over the eastern North Atlantic and Western Europe. Results show that LGM extreme cyclones were characterised by weaker precipitation, enhanced frontal temperature gradients, and stronger wind speeds than PI analogues. These results are in line with the view of a colder and drier Europe, characterised by little vegetation and affected by frequent dust storms, leading to reallocation and build-up of thick loess deposits in Europe.

This article establishes a linkage between the mineral dust cycle and loess deposits during the Last Glacial Maximum (LGM) in Europe. To this aim, we simulate the LGM dust cycle at high resolution using a regional climate-dust model. The model-simulated dust deposition rates are found to be comparable with the mass accumulation rates of the loess deposits determined from more than 70 sites. In contrast to the present-day prevailing westerlies, winds from northeast, east and southeast (36 %) and cyclonic regimes (22 %) were found to prevail over central Europe during the LGM. This supports the hypothesis that the recurring east sector winds associated with a high-pressure system over the Eurasian ice sheet (EIS) dominated the dust transport from the EIS margins in eastern and central Europe. The highest dust emission rates in Europe occurred in summer and autumn. Almost all dust was emitted from the zone between the Alps, the Black Sea and the southern EIS margin. Within this zone, the highest emission rates were located near the southernmost EIS margins corresponding to the present-day German-Polish border region. Coherent with the persistent easterlies, westwards running dust plumes resulted in high deposition rates in western Poland, northern Czechia, the Netherlands, the southern North Sea region and on the North German Plain including adjacent regions in central Germany. The agreement between the climate model simulations and the mass accumulation rates of the loess deposits corroborates the proposed LGM dust cycle hypothesis for Europe.

The spatial distribution and dating of archaeological sites suggest a poor occupation of southern Iberia by hunter-gatherers after the Last Glacial Maximum (LGM) and during Heinrich event 1 (H1) compared to Northern Iberia. The H1 was a period of cold and arid climate conditions and is suspected to have played an important role in the population dynamics in Europe at the end of the Pleistocene. In this study, the potential influence of climate change on the human settlement patterns in Iberia is analysed based on regional palaeoclimate modelling. Here, the WRF model is used to simulate continuous time slices of 30 years of climate conditions representative for both the LGM and H1 at high spatial resolution. The model results indicate that, apart from a general decrease in temperature, a considerable decrease in precipitation over southern Iberia occurred during the H1, that agrees with the available climate proxy data. The analysis of ombrotypes unveils extremely arid conditions, particularly over southern Iberia and during the growing season (summer), which could have constrained the availability of food and water to the inhabitants. The total area in Iberia that can be characterized as ultrahyperarid in summer enlarged from 2% (13 K km2) during the LGM to 22% (148 K km2) during the H1. Likewise, the reconstruction of vegetation types shows an increase of non-arboreal (open shrubland, grassland) types at the expense of arboreal types in southern Iberia for H1. Thus, the different climate conditions and changes in palaeovegetation between the LGM and H1 probably played a major role in the decrease of the hunter-gatherer populations in southern Iberia.

This paper estimates the potential to reduce market-based charging and discharging of a battery energy storage system (BESS) that provides frequency containment reserve (FCR) through (a) the utilization of degrees of freedom (DOFs) during reserve provision, and (b) the utilization of the flexibility of local power units (LPUs) at an investigated industrial site. In context of a of a real BESS providing 7 MW of FCR, the potential is quantified based on a simulation using real grid frequency data and real power profiles of LPUs at an industrial site for the year 2016. At the explored site, LPUs identified to provide charge management of the BESS include wind turbines (WT), a combined heat and power plant (CHPP), and power consumption by the fans of a heating, ventilation and air conditioning (HVAC) system. Results indicate that the energy charged and discharged through market-based transactions can be reduced by 56% and 66% respectively; however, the majority of these reductions are caused by the intelligent use of DOFs. Savings by using the flexibility of the mentioned LPUs can be attributed largely to the flexible operation of the HVAC system due to its highest availability and potential to substitute market-based charge events of the BESS.

We provide an estimate of global vegetation density for the Last Glacial Maximum (LGM) using a simple statistic model. For today's climate, vegetation is divided into 11 vegetation types plus bare soil, for each of which an empirical relationship between the probability of its occurrence and climate controls is derived. The relationships are then used to reconstruct the glacial vegetation patterns with and without considering CO2 modifications. For the LGM, the climate drivers are estimated from an ensemble-average of global paleo-climate simulations. The reconstruction suggests that vegetation types existing in today's cooler and drier regimes prevailed during the LGM and today's desert areas had more vegetation then. The vegetation patterns of the Amazon and Sahara are examined in detail. In the Amazon, tropical rainforest cover is reduced from 80% in today's climate to 40% in the LGM climate. The Sahara was partly covered by shrubs and grassland, with bare ground fraction reduced from 80% today to 30% in the LGM. The reconstructed vegetation patterns are compared with available biome data.